In the Washington Post this morning, we learn that the August 6 PDB was simply one in a series of alarmingly-titled memos:
In April and May 2001, for example, the intelligence community headlined some of those reports “Bin Laden planning multiple operations,” “Bin Laden network’s plans advancing” and “Bin Laden threats are real.”
Somebody was clearly trying to get the attention of a simpleton, and failing.